Process for making acetaldol from acetaldehyde



United States Patent PROCESS FOR MAKING ACETALDOL FROM ACETALDEHYDE Louis Alhritire and Georges Gobron,

signers to Les Usines Saint-Leger-les-Melle, Republic of France Application April 5, 1950, Serial No. 154,021 Claims priority, application France May 23, 1949 7 Claims. (Cl. 260-602 Melle, France, asde Melle (Societe Anonyme), France, a corporation of the This invention relates to the production of acetaldol. Acetaldol is ordinarily produced by condensing acetaldehyde by means The main difiiculty in ing products with consequent fall a temperature of 35 C., a conversion rate of 40% is not to be exceeded, according to this French patent.

preferred temperature of 27 C.30 is thereafter cooled by'water in the 15 C.-30 C. A considerable drawback in the practice of processes such as described in this French patent is that in order to obtain conversion producing large quantities of undesired by-products, the acetaldehyde must remain from 20 in the apparatus. Furthermore, the apparatus is bulky and the fact that the temperatures must be kept low means that a refrigerating unit C. and the mixture subsequent stage at must be included in the possible with respect to its volume and the heat-removzone of about 0.5 to

2 ,713,593 Patented July 19, 1955 system to take care of summer temperatures of the cooling water.

The principal object of the present invention is to avoid at least some of the above-mentioned difiiculties and provide a simple process for time and pressure. In the first zone which includes an elongated path of restricted cross-sectional area, there is caused a continuous flow at a temperature somewhat above 40 C., preferably about C., at a pressure to prevent boiling at such temperature for a period of not over one minute to cause aldolization continuously pass the of the liquid contained in the first 2 kg./cm. sure.

In accordance with our invention, We are able to take advantage of the quickness tion in a very short time and in a very small fraction of The operation is in a reduced space and the reaction is required in prior processes. Thus, the total duration can be and preferably is less than six minutes.

The temperature range of the reaction in the first stage in accordance with our process is preferably from 40 C. to 50 C. and in the second stage from 20 C. to 35 C. Accordingly, there is no difliculty in using running water Without refrigeration even under summertime conditions,

'5 in accordance with our invention.

In operating the process continuously, the heat evolved in the first zone must be removed quickly. For this purpose, the mixture is preferably passed through this first zone so that it offers as large a heat exchange surface as ing fluid employed for the heat exchange is renewed as quickly as possible.

In the preferred embodiment of our invention as shown in the drawing discussed below, the body of acetaldehydeacetaldol-catalyst mixture is circulated rapidly through a system having substantially constant cross section. Thus the system may be and preferably is as shown in the drawings, a narrow piping having a substantially uniform cross section. The circulating mixture is continuously fed with acetaldehyde and aldolization catalyst while a withdrawal of a quantity of mixture corresponding to the feed is efiected. An indirect heat exchange is established between the mixture that circulates through the system and the heat-removing fluid which is preferably water. The speed of circulation of the mixture and the speed of passage of the fluid are regulated with respect to each other and with respect to the rate of feed so that the temperature of the circulating mixture of acetaldehyde, acetaldol and catalyst remains substantially constant at the level in the range at least 40 C. to about 50 C. (first zone) or about 20 C. to 35 C. (second zone). The circulation is further regulated so that the time necessary for the mixture to travel through the first zone does not exceed one minute. The provision of aldolization chambers of substantially uniform cross sec tion insures substantially constant high linear speeds of the circulating mixture throughout the two zones, which has not been the case in prior systems. The heat-removing fluid such as water is circulated through the system which is fed continuously with the cold fluid while a corresponding amount of warm fluid is withdrawn.

For establishing the required pressure of about 0.5 kg./cm.' to 2 kg./cm. any suitable means known in the art may be used such as a pressure of inert gas established on the liquid in the system. However, in accordance with our invention, it is especially advantageous to establish this pressure at least in part as a hydrostatic pressure. For this purpose, as pointed out above, the mixture in the second zone of aldolization which is at a lower temperature is caused to travel upwards. On account of the fact that the time for which the mixture must be maintained at this temperature is relatively long and that the specific weight of the mixture increases as the aldolization progresses, so that the specific weight of the mixture travelling upwardly in the second zone is higher at the top of this zone and lower at the bottom thereof, the length of the piping constituting the second zone may be considerably greater than would be necessary for establishing the required hydrostatic pressure, and it may be advantageous, to avoid too high hydrostatic pressure, to give the piping constituting the second zone a sinuous form.

An apparatus which may be employed in carrying out the above-described process is shown in the accompanying drawing, wherein the figure shows diagrammatically the apparatus employed.

Referring now to this apparatus, a system having a small vertical height is shown at the bottom of the drawing. It has a preferably U-shaped portion designated as 1. The ends of this U-shaped portion are connected by piping 2 leading to a pump 3 for circulating the acetaldehyde-acetaldol-catalyst mixture through 1. Pipe 4 supplies acetaldehyde to pipe 2 and pipe 5 supplies sodium hydroxide solution. The piping 1, 2 and pump 3 constitute the first aldolization zone which includes the aforementioned elongated path of restricted cross-sectional area. Leading from pipe 2 situated as here shown between the lower leg of the U and the pump is a pipe 6 leading upwards through a series of water-jackets to approximately the center of an acidification vessel '7. Acid is added to this vessel through a pipe 8. The vessel is fitted with a vent 9 and from the bottom thereof raw aldol is withdrawn through a pipe 10. Pipe 6 constitutes the second aldolization zone which includes the aforementioned elongated path of restricted cross-sectional of sections area. A pressure of inert gas, such as nitrogen, may be established in vessel 7 when it is desired to establish the required pressure on the mixture in the first stage otherwise than hydrostatically or to increase the hydrostatic pressure on said mixture.

Pipe 1 is covered with a cooling jacket 11 supplied by piping 12 connected at the upper extremity of the U and pipe 13 connected at the lower extremity of the U, each of these pipes being connected to a pump 14 for circulating the water or other cooling fluid through the jacket 11. The pipe 15 is connected near the pump to line 13 for introducing fresh cold water and pipe 16 is connected to line 13 at a point more remote from the pump for removing warm water from the circulating system. Circulation is counterclockwise through the pipe 12, jacket 11, and return pipe 13 to the pump 14.

Piping 6 is also almost completely covered with cooling jackets. As shown in the drawing, this piping 6 has zigzag form and the cooling jacket comprises a number 17, one for each branch of the zigzag piping 6. These sections are interconnected in series by joints 13 and the cooling jacket system is connected to pipe 19 through which water or other cooling fluid flows to the pump 2!) and pipe 21. The pipe 21 joins the last of the series of cooling jackets 17 at the top of the zigzag series. The pipe 19 joins the first or bottom of the jackets 17 at the bottom of the series. The circulation as shown through the water jackets and pump is counterclockwise in this system also. Pipe 22 supplies cold water to this system and pipe 23 withdraws warm water from the system, both being connected to the pipe 19 as shown.

Thermometer 24 is located at the outlet of the lower leg of U-tube 1. Thermometer 25 is located in pipe 6 as it passes into the first of the jackets 17. Thermometer 26 is located in the pipe 6 just beyond the exit of this pipe from the uppermost jacket 17 Thermometers 27 and 28 are provided, respectively, in the cooling systems of the first and second zones and thermometers 29 and 30 are located respectively in the cold water entrance pipes of the first and second zone cooling systems.

Alterations may be made in the above apparatus without departing from the invention; for instance, instead of having single pipes 1 and 6, such pipes may be replaced by a bundle of pipes in each instance.

The following are examples of the process as it may be carried out in connection with the apparatus as described. It is to be understood that the examples are illustrative and the invention is not to be considered as restricted thereto except as indicated in the appended claims.

Example I The first aldolization zone consisting of the interior of piping 1, 2 and pump 3 has a volume of 9 liters. The reaction mixture of acetaldehyde, acetaldol and aldolization catalyst is circulated through this zone, by pump 3, at the rate of about 25 cubic meters per hour. Cooling water is circulated by pump 14 through the cooling system including water-jacket 11, pipe 13, pump 14 and pipe 12 at the rate of 30 cubic meters per hour. Acetaldehyde is fed through pipe 4 into pipe 2 at the rate of 800 liters per hour, i. e., 625 kilograms per hour, and an aqueous solution of sodium hydroxide is fed through pipe 5 into pipe 2 at the rate of 200 liters per hour. This aqueous sodium hydroxide solution contains 1300 grams of sodium hydroxide and is in the form of a 0.65% solution in water. There is thus fed 2.1 grams of sodium hydroxide per kilogram of acetaldehyde.

The temperature as shown on thermometer 24 of the reaction mixture circulating through the first zone is maintained at about 45 C. The temperature as shown on thermometer 29 of the water introduced into the cooling system is 20 C. The temperature as shown on thermometer 27 of the water at the exit from pipe 13 is 38 C. The heat evolved by the reaction is absorbed by the" circulating water, cooling water'being introduced through pipe into the system. The excess of warm water is removed by pipe 16.

The specific weight of the liquid in the first zone is .950 at 45 C. and its content in aldol is 22%, which corresponds to a conversion rate of 29%. The pressure is at about 1 kg./cm. above atmospheric pressure to prevent the reaction mixture from boiling. The time of contact between acetal-dehyde and catalyst in this first zone is 37 seconds.

The second reaction zone consisting of the interior of pipe 6 has a volume of 65 liters. The reaction mixture of acetaldehyde, acetaldol and aldolization catalyst issuing from the first zone ond zone from pipe culated by pump through the cooling system including waterjackets 17, pipe 19, pump 20 and pipe 21 at the rate of 30 cubic meters per hour.

The temperature as shown 'on thermometer 25 of the reaction mixture at the entrance thereof into the jacketed part of pipe 6 is 45.5 thermometer 26 of the reaction mixture at the jacketed part of pipe 6 is 35 as shown on thermometer 30 of the the cooling system is shown on thermometer pipe 19 is 29 C.

The specific weight of the liquid at the exit from the second reaction zone, that is liquid emerging at the upper end of pipe 6 is 1.015 at C. and its content in aldol is 38%, which corresponds to a conversion rate of 50%. The time of contact in the second zone is 4 minutes and seconds.

At the outlet of this second zone, acid is added by pipe 8 in the acidification vessel 7 reaction by reducing the pH The raw aldol is drawn off through pipe 10.

the exit from C. The temperature water introduced into 20 C., and the temperature as 28 of the water at the exit from tion under pressure in the presence of acid, the following raw aldol by circulation through pipe 4.

Example 2 The process is carried out in the same apparatus and in the same manner as in Example 1, the numerical data being the following:

The reaction mixture of acetaldehyde, acetaldol and aldolization catalyst is circulated through the first aldolization zone, by pump 3, at the rate of about 35 cubic meters per hour. is circulated by pump 14 meters per hour. Acetaldehyde is fed at the rate of 1200 The temperature as shown on thermometer 24 is maintained at about C.

The temperature as shown on thermometer 29 is about 15 C. The temperature as shown on thermometer 27 is 35 C.

The specific weight of the liquid in the first zone is .955 at 50 C. and its content in aldol is 30%, which corre- Cooling water is cir- C. The temperature as shown on 7 Pure crotonaldehyde sponds to a conversion rate of 40%. The pressure is maintained at about 1.6 kg./cm. above atmospheric presture. The time of contact between acetaldehyde and catalyst in the first zone is 25 seconds.

Cooling water for the second aldolization zone is circulated by pump 20 at the rate of 30 cubic meters per hour. The temperature as shown on thermometer 25 is about 50 C. The temperature as shown on thermometer 26 is 20 C. The temperature as shown on thermometer 30 is about 15 C. The temperature as shown on the thermometer 28 is 20 C.

The specific weight of the liquid at the exit from the second reaction zone is 1.036 at 20 C. and its content in aldol is 41%, which corresponds to a conversion rate of 55%. The time of contact in the second zone is about 3 minutes and 10 seconds.

The aldolization reaction is stopped as in Example 1. was analyzed by crotonization. One

use of 756 grams of acetaldehyde, gave after crotonization under pressure in analysis:

Unconverted acetaldehyde 340 grams 320 grams (correspond ing to 402 grams of acetaldehyde) Thus, the conversion rate is 55% and the yield is 96.75%.

Example 3 is fed at the rate of 600 liters per hour,

The aqueous soluhydroxide per kilogram of acetaldehyde.

The temperature as shown on thermometer 24 is maintained at 42 C. The temperature as shown on thermometer 29 is about 25 C. The temperature as shown. on thermometer 27 is 37 C.

The specific weight of the liquid in the first zone is .951 at 42 C. and its content in aldol is 17.5%, which corresponds to a conversion rate of 25%. The pressure is maintained at about 0.8 kg./cm. above atmospheric pressure. The time of contact between acetaldehyde and catalyst in the first zone is 45 seconds.

The aldolization reaction is stopped as in Example 1.

by crotonization.

tion under pressure in the presence of acid, the following analysis:

336 grams 285 grams (corresponding to 357 grams of acetaldehyde) The conversion rate is 52% and the yield is 98%.

What we claim is:

1. A continuous process for producing acetaldol which comprises continuously flowing a liquid mixture of acetaldehyde, acetaldol and aldolization catalyst through a first zone, including an elongated path of restricted cross-sectional area, at a temperature between 40 C. and about 45 C. at a pressure to prevent boiling for a period of not over one minute to cause aldolization to begin and continuously passing the so-treated liquid through a second zone, including an elongated path of restricted cross-sectional area, at a temperature materially below 40 C. in the range of about C. to about 35 C. for a period such that the total residence time in said zones does not exceed about 6 minutes 35 seconds.

2. A process in accordance with claim 1 in which substantially a constant volume of liquid is passed through the first zone and is cooled by a heat-removing fluid traveling at a sufiicient rate to maintain a substantially constant temperature in the first zone.

3. A continuous process for producing acetaldol which comprises, continuously flowing a liquid mixture of acetaldehyde, acetaldol and aldolization catalyst through a first zone, including an elongated path of restricted crosssectional area, at a temperature somewhat above 40 C. and in the range up to about 45 C., at a pressure to prevent boiling at such temperature for a period of not over one minute, and passing the so-treated liquid continuously into a second zone, including an elongated path of restricted cross-sectional area, connected directly with the first zone at a temperature materially below 40 C., in the range of about 2 C. to about 35 C. for a period such that the total residence time in said zones does not exceed about 6 minutes 35 seconds, and causing it to flow upwardly above the first zone to a height sufficient to develop the said pressure as hydrostatic pressure in said first zone.

4. A continuous process for producing acetaldol which comprises, continuously flowing a liquid mixture of acetaldehyde, acetaldol and aldolization catalyst through a first zone, including an elongated path of restricted crosssectional area, at a temperature somewhat above 40 C. and in the range up to about 45 C., at a pressure of about 0.5 to 2 kg./cm. above atmospheric pressure for a period of not over one minute to cause aldolization to begin, and passing the so-treated liquid continuously through a sec- Unconverted acetaldehyde Pure crotonaldehyde culated mixture with ond zone directly connected with said first zone, said second zone including an elongated path of restricted crosssectional area, at a temperature materially below 40 C. in the range of about 20 C. to about C. for a period such that the total residence time in said zones does not exceed about 6 minutes 35 seconds.

5. A continuous process for producing acetaldol which comprises, continuously circulating a liquid mixture of acetaldehyde, acetaldol and aldolization catalyst at high speed through a circuit, including an elongated path of restricted, substantially constant cross-sectional area, at a temperature somewhat above C., and in the range up to about C., at a pressure of about 0.5 to 2 kg./cm. above atmospheric pressure, continuously feeding the ciracetaldehyde and aldolization catalyst, continuously passing a quantity of mixture corresponding to the feed upwardly through a zone including an elongated path of substantially the same constant crosssection as the circuit and directly connected with said circuit, at a temperature materially below 40 C., in the range of about 20 C. to about 35 C., to a height to develop said pressure as hydrostatic pressure, and regulating the speed of circulation of the liquid mixture in the circuit and the rate of feed of acetaldehyde and aldolization catalyst so that the time of residence of each part of the liquid mixture does not exceed one minute in said circuit and that the total residence time in said circuit and said zone does not exceed about 6 minutes 35 seconds.

6. The process of claim 5, the temperature in the cycle being controlled by establishing an indirect heat exchange between the circulated mixture and a heat-removing fluid, preferably water.

7. The process of claim 6, said heat-removing fluid being continuously circulated through a heat-removing fluid cycle which is put in indirect heat exchange relationship with the circulated liquid mixture of acetaldehydc, acetaldol and aldolization catalyst, said heat-removing fluid cycle being fed continuously with cold fluid while a corresponding withdrawal of warm fluid is made.

References Cited in the file of this patent UNITED STATES PATENTS 1,075,284 Crockett Oct. 7, 1913 2,375,730 Caldwell et a1 May 8, 1945 2,428,846 Hull Oct. 14, 1947 2,468,710 Hull Apr. 26, 1949 2,489,608 Alheritiere Nov. 29, 1949 2,517,013 Miller et al Aug. 1, 1950 

1. A CONTINUOUS PROCESS FOR PRODUCING ACETALDOL WHICH COMPRISES CONTINOUSLY FLOWING A LIQUID MIXTURE OF ACETALDEHYDE, ACETALDOL AND ALDOLIZATION CATALYST THROUGH A FIRST ZONE, INCLUDING AN ELONGATED PATH OF RESTRICTED CROSS-SECTIONAL AREA, AT A TEMPERATURE BETWEEN 40* C. AND ABOUT 45* C. AT A PRESSURE TO PREVENT BOILING FOR A PERIOD OF NOT OVER ONE MINUTE TO CAUSE ALDOLIZATION TO BEGIN AND CONTINUOUSLY PASSING THE SO-TREATED LIQUID THROUGH A SECOND 